The steamer is a kitchen used cooker that heats the water to generate high temperature steam, and then the food is steamed by the generated high temperature steam. The existing cooker generally includes a steamer cover, a steamer rack, a base, a water tank, an electrically heating element and so on. The steamer rack can be a single layer rack or a multi-layers rack. The existing cooker has the following disadvantages: 1. the bottom layer rack is difficult to be detached from the base due to the steamer rack being placed on the base; 2. it is difficult to mount the top layer rack to the lower layer rack or detach the top layer rack from the lower rack because the top layer rack should align to the lower rack by an alignment structure when stacking the top rack to the lower rack, the rack is difficult to clean because the rack and the rack bottom are integrated as a whole; 3. the water tank is settled on the base that results unsteady of the steamer and further results the water tank is difficult to detached, additionally the water in the water tank is not balanced, this easily dries up the steamer, thereby damaging the steamer and shortening the service time of the steamer.